Accuracy of height on inspire 2

Flyboymedia · Sep 20, 2017

Hello all,

I have recently been approached by a construction company to fly up to an exact elevation and take a few photos in a 360. I was wondering if any one has had experience with this kind of work and could give me some tips on how to increase the accuracy of the elevation.

Flyboymedia · Sep 20, 2017

*edit* The scenario is my client has given me a coordinate which I am to fly to and go to a certain elevation then take stills facing SE.

How would I do this?

ajohnsonlaird · Sep 20, 2017

I suspect that the I2 uses a barometric pressure sensor (because GPS is not particular accurate in the vertical axis and is measured agains the approximate mean sea level of the Earth, see 1-Mean Sea Level, GPS, and the Geoid). I also suspect that you're going to be flying higher than the optical sensors on the I2 can sense the ground.

What you might consider doing is using the I2's pressure height AGL, but make an accurate measurement of some linear feature on the ground (such as the length of a wall, or some straight line). Then you can use that knowledge to scale the images you take. It might not be the best way of proceeding (photogrammetry is a precise science), but it may be good enough. This site might be helpful: Photogrammetry. There's more useful data here: Introduction To UAV Photogrammetry And Lidar Mapping Basics (also mentions DJI sUAVs).

For superior accuracy, I suspect you might have to find a way of using a LIDAR unit (LiDAR Equipped UAVs).

Cheers
Andy

IrishSights · Sep 21, 2017

As it's for taking stills and not surveying the Inspires internal barometer is probably fine. The barometer resets to zero at take off. Download a calibratable barometer app to your phone, calibrate it to get your MSL elevation, set the phone on ground at take off point and take a reading. The combination of this and the Inspires elevation reading will give you what you want.